在硫酸盐氧化酶中对氧原子转移反应性的活性现场立体化学控制
Katrina Peariso1, Rebecca L McNaughton, Martin L Kirk
1Department of Chemistry at The University of New Mexico, Albuquerque, New Mexico 87131-1096, USA.
Journal of the American Chemical Society
|August 1, 2002
概括
计算研究表明,赤道氧原子优先参与硫酸盐氧化酶活性位点内的氧原子转移反应. 这种选择性是由酶的低对称结构驱动的,突出显示了dithiolate连接体的作用.
科学领域:
- 生物化学 生物化学
- 计算化学的计算化学
- 酶的机制 酶的机制
背景情况:
- 硫酸盐氧化酶 (SO) 是一种对硫酸盐代谢至关重要的基多酶.
- 之前的研究使用对称的二氧化 (VI) 复合物建模了氧化SO活性部位.
- 这些模型表明了两个终端oxo捐赠者的电子等价性.
研究的目的:
- 为了研究具有催化能力的硫酸盐氧化酶活性位点的最小模型的电子结构.
- 确定最低无人分子轨道 (LUMO) 的组成,即假定的电子接受器轨道.
- 评估活点几何学在氧原子转移 (OAT) 选择性中的作用.
主要方法:
- 密度函数理论 (DFT) 层面的理论被用于计算研究.
- 使用了一个最小模型,[Mo(VI) O2(S2C2Me2)(SCH3) ]-,具有C1对称性.
- 系统地改变了Oax-Mo-Sthiolate-C扭转角度,以评估其对轨道组成的影响.
主要成果:
- 卢莫主要由一个Mo dxy - ppi* 相互作用组成,其中涉及赤道氧 (Oeq).
- 轴氧 (Oax) 对LUMO没有显著的贡献;LUMO+1具有显著的Oax特征.
- 扭转角度的变化始终显示出Oeq主导的LUMO特征,证实了Oeq对OAT的选择性.
结论:
- 氧化SO活性位点的低对称结构决定了氧原子的选择和激活.
- -1,2-二甲基酸对促进OAT反应性通过对赤道氧 donor的动态转变效应起着关键作用.
- 计算发现支持硫酸盐氧化酶中氧原子转移的特定机制.
相关概念视频
The Equilibrium Constant
Consider the oxidation of sulfur dioxide:
Catalytically Perfect Enzymes
The theory of catalytically perfect enzymes was first proposed by W.J. Albery and J. R. Knowles in 1976. These enzymes catalyze biochemical reactions at high-speed. Their catalytic efficiency values range from 108-109 M-1s-1. These enzymes are also called 'diffusion-controlled' as the only rate-limiting step in the catalysis is that of the substrate diffusion into the active site. Examples include triose phosphate isomerase, fumarase, and superoxide dismutase.
Introduction to Mechanisms of Enzyme Catalysis
For many years, scientists thought that enzyme-substrate binding took place in a simple "lock-and-key" fashion. This model stated that the enzyme and substrate fit together perfectly in one instantaneous step. However, current research supports a more refined view scientists call induced fit. The induced-fit model expands upon the lock-and-key model by describing a more dynamic interaction between enzyme and substrate. As the enzyme and substrate come together, their interaction causes a mild...
Catalysis
Catalysis influences the rate of chemical reactions by providing an alternative reaction pathway with lower activation energy. A catalyst speeds up a reaction, but it is not consumed during the process. The fundamental principle of catalysis is the ability of a catalyst to alter the reaction mechanism, often introducing a more efficient pathway than the uncatalyzed process.In a catalyzed reaction, the catalyst participates directly in the reaction mechanism. It interacts with reactants to form...
Heterogeneous Catalysis
Heterogeneous catalysis involves a catalyst in a different phase from the reactants. It is a process where the catalyst and the reactants are in distinct phases, typically solid and gas or liquid.Most heterogeneous catalysts are metals, metal oxides, or acids. The list includes transition metals like iron (Fe), cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), manganese (Mn), tungsten (W), silver (Ag), and copper (Cu). These metals possess partially vacant d orbitals that...
Carbon-dioxide Fixation
Carbon dioxide fixation in prokaryotes enables the assimilation of inorganic carbon into organic molecules, supporting biosynthetic pathways, sustaining ecosystems, and contributing to the global carbon cycle. It also has industrial applications in carbon capture and bioproduct synthesis. Autotrophic organisms rely on this process to utilize CO₂ as a carbon source in diverse environments.The Calvin CycleThe Calvin cycle is the most widespread carbon fixation mechanism, primarily used by...


